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Platero-Prats AE, Mavrandonakis A, Liu J, Chen Z, Chen Z, Li Z, Yakovenko AA, Gallington LC, Hupp JT, Farha OK, Cramer CJ, Chapman KW. The Molecular Path Approaching the Active Site in Catalytic Metal-Organic Frameworks. J Am Chem Soc 2021; 143:20090-20094. [PMID: 34826220 DOI: 10.1021/jacs.1c11213] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
How molecules approach, bind at, and release from catalytic sites is key to heterogeneous catalysis, including for emerging metal-organic framework (MOF)-based catalysts. We use in situ synchrotron X-ray scattering analysis to evaluate the dominant binding sites for reagent and product molecules in the vicinity of catalytic Ni-oxo clusters in NU-1000 with different surface functionalization under conditions approaching those used in catalysis. The locations of the reagent and product molecules within the pores can be linked to the activity for ethylene hydrogenation. For the most active catalyst, ethylene reagent molecules bind close to the catalytic clusters, but only at temperatures approaching experimentally observed onset of catalysis. The ethane product molecules favor a different binding location suggesting that the product is readily released from the active site. An unusual guest-dependence of the framework negative thermal expansion is documented. We hypothesize that reagent and product binding sites reflect the pathway through the MOF to the active site and can be used to identify key factors that impact the catalytic activity.
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Lu Z, Du L, Guo R, Zhang G, Duan J, Zhang J, Han L, Bai J, Hupp JT. Double-Walled Zn 36@Zn 104 Multicomponent Senary Metal-Organic Polyhedral Framework and Its Isoreticular Evolution. J Am Chem Soc 2021; 143:17942-17946. [PMID: 34665599 DOI: 10.1021/jacs.1c08286] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Metal-organic polyhedral frameworks are attractive in gas storage and separation due to large voids with windows that can serve as traps for guest molecules. Introducing multivariant/multicomponent functionalities in them are ways of improving performances for certain targets. The high compatibility of organic linkers can generate multivariant MOFs, but by far, the diversity of secondary building units (SBUs) in a single metal-organic framework is still limited (no more than two in most cases). Here we report a new double-walled Zn36@Zn104 metal-organic polyhedral framework (HHU-8) with five types of topologically distinct SBUs and its isoreticular evolution to the Zn36@Zn136 counterpart (HHU-8s). Both MOFs are the first to be constructed with such high numbers of topologically distinct SBUs as well as topologically distinct nodes, and their formation and evolution provide new insight into SBU's controllability.
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Audu CO, Chen D, Kung CW, Snurr RQ, Nguyen ST, Farha OK, Hupp JT. Transport Diffusion of Linear Alkanes (C 5-C 16) through Thin Films of ZIF-8 as Assessed by Quartz Crystal Microgravimetry. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2021; 37:9405-9414. [PMID: 34338528 DOI: 10.1021/acs.langmuir.1c00672] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
We report uptake capacities and transport diffusivities, D, for each of eight linear alkanes (ranging from C5 to C16) in quartz crystal-supported films of solvent-evacuated ZIF-8. Analyses of the alkane uptake profiles revealed that the transport dynamics are governed by guest diffusion through metal-organic framework (MOF) (ZIF-8) crystallites rather than by rates of entry into films at the MOF/vapor interface. The obtained diffusivities range from just over 10-18 m2/s to just under 10-14 m2/s. Notably, minimum cross-sectional widths for all guests exceed the crystallographically measured width of ZIF-8's largest apertures and imply consistently with previous experimental and computational studies that apertures expand to accommodate guest uptake. On average, each additional carbon decreases the transport diffusivity of an alkane by twofold. Closer examination, however, reveals an odd-even effect such that linear alkanes having even numbers of carbons diffuse more rapidly than alkanes featuring one more or one less carbon atom. Thus, ZIF-8's differentiation of transport diffusivities for pairs of alkanes differing in length by only one carbon atom can be significantly greater than the aforementioned factor of 2. Elucidation of the microscopic basis for the odd-even behavior, however, awaits the outcome of molecular dynamics calculations that are beyond the scope of the present study. For compact, solvothermally prepared films, guest transport is dominated by 1D diffusion from the film/vapor interface and toward the underlying quartz crystal. For much lower density, electrophoretically deposited (EPD) films, crystallites behave nearly independently, and guest transport can be adequately modeled by assuming rapid permeation of macroscopic voids between crystallites, followed by entry and rate-limiting radial diffusion into isolated crystallites. One consequence is that EPD films can be much more rapidly infiltrated by molecular guests than can compact, solvothermally grown films. The combined results have potentially favorable implications for the development of kinetic separation schemes for closely related analytes.
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Yang Y, Noh H, Ma Q, Wang R, Chen Z, Schweitzer NM, Liu J, Chapman KW, Hupp JT. Engineering Dendrimer-Templated, Metal-Organic Framework-Confined Zero-Valent, Transition-Metal Catalysts. ACS APPLIED MATERIALS & INTERFACES 2021; 13:36232-36239. [PMID: 34308623 DOI: 10.1021/acsami.1c11541] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
We describe and experimentally illustrate a strategy for synthesizing reactant-accessible, supported arrays of well-confined, sub-nanometer to 2 nm, metal(0) clusters and particles-here, copper, palladium, and platinum. The synthesis entails (a) solution-phase binding of metal ions by a generation-2 poly(amidoamine) (PAMAM) dendrimer, (b) electrostatic uptake of metalated, solution-dissolved, and positively charged dendrimers by the negatively charged pores of a zirconium-based metal-organic framework (MOF), NU-1000, and (c) chemical reduction of the incorporated metal ions. The pH of the unbuffered solution is known to control the overall charges of both the dendrimer guests and the hierarchically porous MOF. The combined results of electron microscopy, X-ray spectroscopy, and other measurements indicate the formation and microscopically uniform spatial distributions of zero-valent, monometallic Cu, Pd, and Pt species, with sizes depending strongly on the conditions and methods used for reduction of incorporated metal ions. Access to sub-nanometer clusters is ascribed to the stabilization effects imposed by the two templates (i.e., NU-1000 and dendrimer), which significantly limit the extent to which the metal atoms aggregate; as the thermal input increases, the dendrimer template gradually decomposes, allowing a further aggregation of metal clusters inside the hexagonal mesoporous channel of the MOF template, which ultimately self-limits at 3 nm (i.e., the mesopore width of NU-1000). Using CO oxidation and n-hexene hydrogenation as model reactions in the gas and condensed phases, we show that the dual-templated metal species can act as stable, efficient heterogeneous catalysts.
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Fu X, Liu J, Kanchanakungwankul S, Hu X, Yue Q, Truhlar DG, Hupp JT, Kang Y. Two-Dimensional Pd Rafts Confined in Copper Nanosheets for Selective Semihydrogenation of Acetylene. NANO LETTERS 2021; 21:5620-5626. [PMID: 34170691 DOI: 10.1021/acs.nanolett.1c01124] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
The development of highly selective and active catalysts to catalyze an industrially important semihydrogenation reaction remains an open challenge. Here, we report the design of a bimetallic Pd/Cu(111) catalyst with Pd rafts confined in a Cu nanosheet, which exhibits desirable catalytic performance for acetylene semihydrogenation to ethylene with the selectivity of >90%. Theory calculations show that Pd atoms replacing neighboring Cu atoms in Cu(111) can improve the catalytic activity by reducing the energy barrier of the semihydrogenation reaction, as compared to unsubstituted Cu(111), and can improve the selectivity by weakening the adsorption of C2H4, as compared to a Pd(111) surface. The presence of Pd rafts confined in Cu nanosheets effectively turns on Cu nanosheets for semihydrogenation of acetylene with high activity and selectivity under mild reaction conditions. This work offers a well-defined nanostructured Pd/Cu(111) model catalyst that bridges the pressure and materials' gap between surface-science catalysis and practical catalysis.
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Liu J, Chen Z, Wang R, Alayoglu S, Islamoglu T, Lee SJ, Sheridan TR, Chen H, Snurr RQ, Farha OK, Hupp JT. Zirconium Metal-Organic Frameworks Integrating Chloride Ions for Ammonia Capture and/or Chemical Separation. ACS APPLIED MATERIALS & INTERFACES 2021; 13:22485-22494. [PMID: 33961384 DOI: 10.1021/acsami.1c03717] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Ammonia capture by porous materials is relevant to protection of humans from chemical threats, while ammonia separation may be relevant to its isolation and use following generation by emerging electrochemical schemes. Our previous work described both reversible and irreversible interactions of ammonia with the metal-organic framework (MOF) material, NU-1000, following thermal treatment at either 120 or 300 °C. In the present work, we have examined NU-1000-Cl, a variant that features a modified node structure-at ambient temperature, Zr6(μ3-O)4(μ3-OH)4(H2O)812+ in place of Zr6(μ3-O)4(μ3-OH)4(OH)4(H2O)48+. Carboxylate termini from each of eight linkers balance the 8+ charge of the parent node, while four chloride ions, attached only by hydrogen bonding, complete the charge balance for the 12+ version. We find that both reversible and irreversible uptake of ammonia are enhanced for NU-1000-Cl, relative to the chloride-free version. Two irreversible interactions were observed via in situ diffuse-reflectance infrared Fourier-transform spectroscopy: coordination of NH3 at open Zr sites generated during thermal pretreatment and formation of NH4+ by proton transfer from node aqua ligands. The irreversibility of the latter appears to be facilitated by the presence chloride ions, as NH4+ formation occurs reversibly with chloride-free NU-1000. At room temperature, chemically reversible (and irreversible) interactions between ammonia and NU-1000-Cl result in separation of NH3 from N2 when gas mixtures are examined with breakthrough instrumentation, as evinced by a much longer breakthrough time (∼9 min) for NH3.
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Liu J, Lu Z, Chen Z, Rimoldi M, Howarth AJ, Chen H, Alayoglu S, Snurr RQ, Farha OK, Hupp JT. Ammonia Capture within Zirconium Metal-Organic Frameworks: Reversible and Irreversible Uptake. ACS APPLIED MATERIALS & INTERFACES 2021; 13:20081-20093. [PMID: 33886253 DOI: 10.1021/acsami.1c02370] [Citation(s) in RCA: 21] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Ammonia uptake by high-capacity and high-porosity sorbents is a promising approach to its storage and release, capture and mitigation, and chemical separation. Here, we examined the ammonia sorption behavior of several versions of an archetypal zirconium-based metal-organic framework (MOF) material, NU-1000-a meso- and microporous crystalline compound having the empirical formula (1,3,6,8-tetrakis(p-benzoate)pyrene)2 Zr6(μ3-O)4(μ3-OH)4(H2O)4(OH)4 with linkers and nodes arranged to satisfy a csq topology. Depending on the thermal treatment protocol used prior to sorption measurements, ammonia can physisorb to NU-1000 via hydrogen-bonding and London-dispersion interactions and chemisorb via Brønsted acid-base reactions with node-integrated proton donors (μ3-hydroxos) and node-ligated proton donors (terminal hydroxos), via simple coordination at open Zr(IV) sites, or via dissociative coordination to Zr(IV) as NH2- and protonation of a node-based μ3-oxo. Ammonia adsorption occurs via both reversible and irreversible processes. The latter are of particular interest for protection and mitigation. Notably, the unexpected dissociative adsorption occurs only with nodes that have been fully dehydrated and irreversibly structurally distorted via thermal pre-treatment-a finding that is supported by density functional theory calculations. Differentiating and ranking the relative importance of the many modes of adsorption was facilitated, in part, by the availability of variants of NU-1000 that replace the majority of terminal aqua and hydroxo ligands with nonstructural formate ligands, auxiliary ditopic linkers, or both. The study provides insights into the chemical basis for both reversible and irreversible uptake of ammonia by Zr-MOFs and related compounds. The unexpectedly rich variety of sorption motifs suggest the criteria for designing or choosing MOFs that are optimal for specific ammonia-centric applications.
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Lu Z, Wang R, Liao Y, Farha OK, Bi W, Sheridan TR, Zhang K, Duan J, Liu J, Hupp JT. Isomer of linker for NU-1000 yields a new she-type, catalytic, and hierarchically porous, Zr-based metal-organic framework. Chem Commun (Camb) 2021; 57:3571-3574. [PMID: 33704273 DOI: 10.1039/d0cc07974j] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
The well-known MOF (metal-organic framework) linker tetrakis(p-benzoate)pyrene (TBAPy4-) lacks steric hindrance between its benzoates. Changing the 1,3,6,8-siting of benzoates in TBAPy4- to 4,5,9,10-siting introduces substantial steric hindrance and, in turn, enables the synthesis of a new hierarchically porous, she-type MOF Zr6(μ3-O)4(μ3-OH)4(C6H5COO)3(COO)3(TBAPy-2)3/2 (NU-601), where TBAPy-24- is the 4,5,9,10 isomer of TBAPy4-. NU-601 shows high catalytic activity for degradative hydrolysis of a simulant for G-type fluoro-phosphorus nerve agents.
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Roy I, Goswami S, Young RM, Schlesinger I, Mian MR, Enciso AE, Zhang X, Hornick JE, Farha OK, Wasielewski MR, Hupp JT, Stoddart JF. Photon Upconversion in a Glowing Metal–Organic Framework. J Am Chem Soc 2021; 143:5053-5059. [DOI: 10.1021/jacs.1c00298] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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Lancheros A, Goswami S, Mian MR, Zhang X, Zarate X, Schott E, Farha OK, Hupp JT. Modulation of CO 2 adsorption in novel pillar-layered MOFs based on carboxylate-pyrazole flexible linker. Dalton Trans 2021; 50:2880-2890. [PMID: 33544103 DOI: 10.1039/d0dt03166f] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Metal-organic frameworks (MOFs) have attracted significant attention as sorbents due to their high surface area, tunable pore volume and pore size, coordinatively unsaturated metal sites, and ability to install desired functional groups by post-synthetic modification. Herein, we report three new MOFs with pillar-paddlewheel structures that have been synthesized solvothermally from the mixture of the carboxylate-pyrazole flexible linker (H2L), 4,4-bipyridine (BPY)/triethylenediamine (DABCO), and Zn(ii)/Cu(ii) ions. The MOFs obtained, namely [ZnII(L)BPY], [CuII(L)BPY], and [CuII(L)DABCO], exhibit two-fold interpenetration and dinuclear paddle-wheel nodes. The Zn(ii)/Cu(ii) cations are coordinated by two equatorial L linkers that result in two-dimensional sheets which in turn are pillared by BPY or DABCO in the perpendicular direction to obtain a neutral three-dimensional framework that shows one-dimensional square channels. The three pillar-layered MOFs were characterized as microporous materials showing high crystalline stability after activation at 120 °C and CO2 adsorption. All MOFs contain uncoordinated Lewis basic pyrazole nitrogen atoms in the framework which have an affinity toward CO2 and hence could potentially serve as CO2 adsorption material. The CO2 uptake capacity was initially enhanced by replacing Zn with Cu and then replacing the pillar, going from BPY to DABCO. Overall, all the MOFs exhibit low isosteric heat (Qst) of adsorption which signifies an advantage due to the energy required for the adsorption and regeneration processes.
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Otake KI, Ahn S, Knapp J, Hupp JT, Notestein JM, Farha OK. Vapor-Phase Cyclohexene Epoxidation by Single-Ion Fe(III) Sites in Metal-Organic Frameworks. Inorg Chem 2021; 60:2457-2463. [PMID: 33497212 DOI: 10.1021/acs.inorgchem.0c03364] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Heterogeneous catalysts supported on metal-organic frameworks (MOFs), which possess uniform porosity and crystallinity, have attracted significant interest for recent years due to the ease of active-site characterization via X-ray diffraction and the subsequent relation of the active site structure to the catalytic activity. We report the syntheses, structures, and oxidation catalytic activities of single-ion iron catalysts incorporated into the zirconium MOF NU-1000. Single-ion iron catalysts with different counteranions were anchored onto the Zr node through postsynthetic solvothermal deposition. Crystallographic characterization of the resulting MOFs (NU-1000-Fe-Cl and NU-1000-Fe-NO3) revealed that, while both frameworks have similar Fe coordination, the distance between Fe and the Zr6 node differs significantly between the two. The product rate profiles of the two catalysts for vapor-phase cyclohexene epoxidation demonstrate different initial rates and product formations, likely originating from the different Fe-O distances.
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Chen Y, Zhang X, Mian MR, Son FA, Zhang K, Cao R, Chen Z, Lee SJ, Idrees KB, Goetjen TA, Lyu J, Li P, Xia Q, Li Z, Hupp JT, Islamoglu T, Napolitano A, Peterson GW, Farha OK. Structural Diversity of Zirconium Metal-Organic Frameworks and Effect on Adsorption of Toxic Chemicals. J Am Chem Soc 2020; 142:21428-21438. [PMID: 33290083 DOI: 10.1021/jacs.0c10400] [Citation(s) in RCA: 62] [Impact Index Per Article: 15.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
While linkers with various conformations pose challenges in the design and prediction of metal-organic framework (MOF) structures, they ultimately provide great opportunities for the discovery of novel structures thereby enriching structural diversity. Tetratopic carboxylate linkers, for example, have been widely used in the formation of Zr-based MOFs due to the ability to target diverse topologies, providing a promising platform to explore their mechanisms of formation. However, it remains a challenge to control the resulting structures when considering the complex assembly of linkers with unpredicted conformations and diverse Zr6 node connectivities. Herein, we systematically explore how solvents and modulators employed during synthesis influence the resulting topologies of Zr-MOFs, choosing H4TCPB-Br2 (1,4-dibromo-2,3,5,6-tetrakis(4-carboxyphenyl)benzene) as a representative tetratopic carboxylate linker. By modulating the reaction conditions, the conformations of the linker and the connectivities of the Zr6 node can be simultaneously tuned, resulting in four types of structures: a new topology (NU-500), she (NU-600), scu (NU-906), and csq (NU-1008). Importantly, we have synthesized the first 5-connected Zr6 node to date with the (4,4,4,5)-connected framework, NU-500. We subsequently performed detailed structural analyses to uncover the relationship between the structures and topologies of these MOFs and demonstrated the crucial role that the flexible linker played to access varied structures by different degrees of linker deformation. Due to a variety of pore structures ranging from micropores to hierarchical micropores and mesopores, the resulting MOFs show drastically different behaviors for the adsorption of n-hexane and dynamic adsorption of 2-chloroethyl ethyl sulfide (CEES) under dry and humid conditions.
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Yang Y, Zhang X, Kanchanakungwankul S, Lu Z, Noh H, Syed ZH, Farha OK, Truhlar DG, Hupp JT. Unexpected “Spontaneous” Evolution of Catalytic, MOF-Supported Single Cu(II) Cations to Catalytic, MOF-Supported Cu(0) Nanoparticles. J Am Chem Soc 2020; 142:21169-21177. [DOI: 10.1021/jacs.0c10367] [Citation(s) in RCA: 38] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
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Lu Z, Liu J, Zhang X, Liao Y, Wang R, Zhang K, Lyu J, Farha OK, Hupp JT. Node-Accessible Zirconium MOFs. J Am Chem Soc 2020; 142:21110-21121. [PMID: 33263388 DOI: 10.1021/jacs.0c09782] [Citation(s) in RCA: 64] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
High-stability, zirconium-based metal-organic frameworks are attractive as heterogeneous catalysts and as model supports for uniform arrays of subsequently constructed heterogeneous catalysts-for example, MOF-node-grafted metal-oxy and metal-sulfur clusters. For hexa-Zr(IV)-MOFs characterized by nodes that are less than 12-connected, sites not used for linkers are ideally occupied by reactive and displaceable OH/H2O pairs. The desired pairs are ideal for grafting the aforementioned catalytic clusters, while aqua-ligand lability renders them effective for exposing highly Lewis-acidic Zr(IV) sites (catalytic sites) to candidate reactants. New single-crystal X-ray studies of an eight-connected Zr-MOF, NU-1000, reveal that conventional activation fully removes modulator ligands, but replaces them with three node-blocking formate ligands (from solvent decomposition) and only one OH/H2O pair, not four-a largely overlooked complication that now appears to be general for Zr-MOFs. Here we describe an alternative activation protocol that effectively removes modulators, avoids formate, and installs the full complement of terminal OH/H2O pairs. It does so via an unusual isolatable intermediate featuring eight aqua ligands and four non-ligated chlorides-again as supported by single-crystal X-ray data. We find that complete replacement of node-blocking modulators/formate with the originally envisioned OH/OH2 pairs has striking consequences; here we touch upon just three. First, elimination of unrecognized formate renders aqua ligands much more thermally labile, enabling open Zr(IV) sites to be obtained at lower temperature. Second, in the absence of formate, which otherwise links and locks pairs of node Zr(IV) ions, reversible removal of aqua ligands engenders reversible contraction of MOF meso- and micropores, as evidenced by X-ray diffraction. Third, formate replacement with OH/OH2 pairs renders NU-1000 ca.10× more active for catalytic hydrolytic degradation of a representative simulant of G-type chemical warfare agents.
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Nagatomi H, Gallington LC, Goswami S, Duan J, Chapman KW, Yanai N, Kimizuka N, Farha OK, Hupp JT. Regioselective Functionalization of the Mesoporous Metal-Organic Framework, NU-1000, with Photo-Active Tris-(2,2'-bipyridine)ruthenium(II). ACS OMEGA 2020; 5:30299-30305. [PMID: 33251464 PMCID: PMC7689908 DOI: 10.1021/acsomega.0c04823] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 10/01/2020] [Accepted: 10/29/2020] [Indexed: 06/12/2023]
Abstract
Solvent-assisted ligand incorporation is an excellent method for the post-synthetic functionalization of Zr-based metal-organic frameworks (MOFs), as carboxylate-derivative functionalities readily coordinate to the Zr6 nodes by displacing node-based aqua and terminal hydroxo ligands. In this study, a photocatalytically active ruthenium complex RuII(bpy)2(dcbpy), that is, bis-(2,2'-bipyridine)-(4,4'-dicarboxy-2,2'-bipyridine)ruthenium, was installed in the mono-protonated (carboxylic acid) form within NU-1000 via SALI. Crystallographic information regarding the siting of the ruthenium complex within the MOF pores is obtained by difference envelope density analysis. The ruthenium-functionalized MOF, termed Ru-NU-1000, shows excellent heterogeneous photocatalytic activity for an oxidative amine coupling reaction.
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Atilgan A, Cetin MM, Yu J, Beldjoudi Y, Liu J, Stern CL, Cetin FM, Islamoglu T, Farha OK, Deria P, Stoddart JF, Hupp JT. Post-Synthetically Elaborated BODIPY-Based Porous Organic Polymers (POPs) for the Photochemical Detoxification of a Sulfur Mustard Simulant. J Am Chem Soc 2020; 142:18554-18564. [PMID: 32981316 DOI: 10.1021/jacs.0c07784] [Citation(s) in RCA: 48] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
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Wang R, Bukowski BC, Duan J, Sheridan TR, Atilgan A, Zhang K, Snurr RQ, Hupp JT. Investigating the Process and Mechanism of Molecular Transport within a Representative Solvent-Filled Metal-Organic Framework. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2020; 36:10853-10859. [PMID: 32841562 DOI: 10.1021/acs.langmuir.0c01999] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Effective permeation into, and diffusive mass transport within, solvent-filled metal-organic frameworks (MOFs) is critical in applications such as MOF-based chemical catalysis of condensed-phase reactions. In this work, we studied the entry from solution of a luminescent probe molecule, 1,3,5,7-tetramethyl-4,4-difluoroboradiazaindacene (BODIPY), into the 1D channel-type, zirconium-based MOF NU-1008 and subsequent transport of the probe through the MOF. Measurements were accomplished via in situ confocal fluorescence microscopy of individual crystallites, where the evolution of the fluorescence response from the crystallite was followed as functions of both time and location within the crystallite. From the confocal data, intracrystalline transport of BODIPY is well-described by one-dimensional diffusion along the channel direction. Varying the chemical identity of the solvent revealed an inverse dependence of probe-molecule diffusivity on bulk-solvent viscosity, qualitatively consistent with expectations from the Stokes-Einstein equation for molecular diffusion. At a more quantitative level, however, measured diffusion coefficients are about 100-fold smaller than expected from Stokes-Einstein, pointing to substantial channel-confinement effects. Evaluation of the confocal data also reveals a non-negligible mass transport resistance, i.e., surface barrier, associated with the probe molecule leaving the solution and permeating the exterior surface of the MOF. Permeation by the probe entails displacement of solvent from the MOF channels. The magnitude of the resistance increases with the size of the solvent molecule. This work draws attention to the importance of MOF structure, external-surface barriers, and solvent molecule identity to the overall transport process in MOFs, which should assist in understanding the performance of MOFs in applications such as condensed-phase heterogeneous catalysis.
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Goetjen TA, Liu J, Wu Y, Sui J, Zhang X, Hupp JT, Farha OK. Metal-organic framework (MOF) materials as polymerization catalysts: a review and recent advances. Chem Commun (Camb) 2020; 56:10409-10418. [PMID: 32745156 DOI: 10.1039/d0cc03790g] [Citation(s) in RCA: 99] [Impact Index Per Article: 24.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Synthetic polymers are ubiquitous across both the industrial and consumer segments of the world economy. Catalysts enable rapid, efficient, selective, and even stereoselective, formation of desired polymers from any of a host of candidate monomers. While numerous molecular catalysts have been shown to be effective for these reactions, separation of the catalysts from reaction products is typically difficult - a potentially problematic complication that suggests instead the use of heterogeneous catalysts. Many of the most effective heterogeneous catalysts, however, comprise supported collections of reaction centres that are decidedly nonuniform in their composition, siting, and activity. Nonuniformity complicates atomic-scale evaluation of the basis for catalytic activity and thus impedes scientific hypothesis-driven understanding and development of superior catalysts. In view of the fundamental desirability of structural and chemical uniformity at the meso, nano, and even atomic scale, crystallographically well-defined, high-porosity metal-organic frameworks (MOFs) have attracted attention as model catalysts and/or catalyst-supports for a wide variety of chemical transformations. In the realm of synthetic polymers, catalyst-functionalized MOFs have been studied for reactions ranging from coordination-mediated polymerization of ethylene to visible-light initiated radical polymerizations. Nevertheless, many polymerization reactions remain to be explored - and, no doubt, will be explored, given the remarkable structural and compositional diversity of attainable MOFs. Noteworthy emerging studies include work directed toward more sophisticated catalytic schemes such as polymer templating using MOF pore architectures and tandem copolymerizations using MOF-supported reaction centres. Finally, it is appropriate to recognize that MOFs themselves are synthetic polymers - albeit, uncoventional ones.
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Beldjoudi Y, Atilgan A, Weber JA, Roy I, Young RM, Yu J, Deria P, Enciso AE, Wasielewski MR, Hupp JT, Stoddart JF. Supramolecular Porous Organic Nanocomposites for Heterogeneous Photocatalysis of a Sulfur Mustard Simulant. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2020; 32:e2001592. [PMID: 32602131 DOI: 10.1002/adma.202001592] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/05/2020] [Revised: 06/01/2020] [Indexed: 06/11/2023]
Abstract
Efficient heterogeneous photosensitizing materials require both large accessible surface areas and excitons of suitable energies and with well-defined spin structures. Confinement of the tetracationic cyclophane (ExBox4+ ) within a nonporous anionic polystyrene sulfonate (PSS) matrix leads to a surface area increase of up to 225 m2 g-1 in ExBox•PSS. Efficient intersystem crossing is achieved by combining the spin-orbit coupling associated to Br heavy atoms in 1,3,5,8-tetrabromopyrene (TBP), and the photoinduced electron transfer in a TBP⊂ExBox4+ supramolecular dyad. The TBP⊂ExBox4+ complex displays a charge transfer band at 450 nm and an exciplex emission at 520 nm, indicating the formation of new mixed-electronic states. The lowest triplet state (T1 , 1.89 eV) is localized on the TBP and is close in energy with the charge separated state (CT, 2.14 eV). The homogeneous and heterogeneous photocatalytic activities of the TBP⊂ExBox4+ , for the elimination of a sulfur mustard simulant, has proved to be significantly more efficient than TBP and ExBox+4 , confirming the importance of the newly formed excited-state manifold in TBP⊂ExBox4+ for the population of the low-lying T1 state. The high stability, facile preparation, and high performance of the TBP⊂ExBox•PSS nanocomposites augur well for the future development of new supramolecular heterogeneous photosensitizers using host-guest chemistry.
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Wang X, Zhang X, Pandharkar R, Lyu J, Ray D, Yang Y, Kato S, Liu J, Wasson MC, Islamoglu T, Li Z, Hupp JT, Cramer CJ, Gagliardi L, Farha OK. Insights into the Structure–Activity Relationships in Metal–Organic Framework-Supported Nickel Catalysts for Ethylene Hydrogenation. ACS Catal 2020. [DOI: 10.1021/acscatal.0c01844] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
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Kung CW, Goswami S, Hod I, Wang TC, Duan J, Farha OK, Hupp JT. Charge Transport in Zirconium-Based Metal-Organic Frameworks. Acc Chem Res 2020; 53:1187-1195. [PMID: 32401008 DOI: 10.1021/acs.accounts.0c00106] [Citation(s) in RCA: 70] [Impact Index Per Article: 17.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Metal-organic frameworks (MOFs) are a class of crystalline porous materials characterized by inorganic nodes and multitopic organic linkers. Because of their molecular-scale porosity and periodic intraframework chemical functionality, MOFs are attractive scaffolds for supporting and/or organizing catalysts, photocatalysts, chemical-sensing elements, small enzymes, and numerous other functional-property-imparting, nanometer-scale objects. Notably, these objects can be installed after the synthesis of the MOF, eliminating the need for chemical and thermal compatibility of the objects with the synthesis milieu. Thus, postsynthetically functionalized MOFs can present three-dimensional arrays of high-density, yet well-separated, active sites. Depending on the application and corresponding morphological requirements, MOF materials can be prepared in thin-film form, pelletized form, isolated single-crystal form, polycrystalline powder form, mixed-matrix membrane form, or other forms. For certain applications, most obviously catalytic hydrolysis and electro- or photocatalytic water splitting, but also many others, an additional requirement is water stability. MOFs featuring hexa-zirconium(IV)-oxy nodes satisfy this requirement. For applications involving electrocatalysis, charge storage, photoelectrochemical energy conversion, and chemiresistive sensing, a further requirement is electrical conductivity, as embodied in electron or hole transport. As most MOFs, under most conditions, are electrically insulating, imparting controllable charge-transport behavior is both a chemically intriguing and chemically compelling challenge.Herein, we describe three strategies to render zirconium-based metal-organic frameworks (MOFs) tunably electrically conductive and, therefore, capable of transporting charge on the few nanometers (i.e., several molecular units) to few micrometers (i.e., typical dimensions for MOF microcrystallites) scale. The first strategy centers on redox-hopping between periodically arranged, chemically equivalent sites, essentially repetitive electron (or hole) self-exchange. Zirconium nodes are electrically insulating, but they can function as grafting sites for (a) redox-active inorganic clusters or (b) molecular redox couples. Alternatively, charge hopping based on linker redox properties can be exploited. Marcus's theory of electron transfer has proven useful for understanding/predicting trends in redox-hopping based conductivity, most notably, in accounting for variations as great as 3000-fold depending on the direction of charge propagation through structurally anisotropic MOFs. In MOF environments, propagation of electronic charge via redox hopping is necessarily accompanied by movement of charge-compensating ions. Consequently, rates of redox hopping can depend on both the identity and concentration of ions permeating the MOF. In the context of electrocatalysis, an important goal is to transport electronic charge fast enough to match or exceed the inherent activity of MOF-based or MOF-immobilized catalysts.Bandlike electronic conductivity is the focus of an alternative strategy: one based on the introduction of molecular guests capable of forming donor-acceptor charge transfer complexes with the host framework. Theory again can be applied predictively to alter conductivity. A third strategy similarly emphasizes electronic conductivity, but it makes use of added bridges in the form of molecular oligomers or inorganic clusters that can then be linked to span the length of a MOF crystallite. For all strategies, retention of molecular-scale porosity is emphasized, as this property is key to many applications. Finally, while our focus is on Zr-MOFs, the described approaches clearly are extendable to other MOF compositions, as has already been demonstrated, in part, in studies by others.
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Kirlikovali KO, Chen Z, Islamoglu T, Hupp JT, Farha OK. Zirconium-Based Metal-Organic Frameworks for the Catalytic Hydrolysis of Organophosphorus Nerve Agents. ACS APPLIED MATERIALS & INTERFACES 2020; 12:14702-14720. [PMID: 31951378 DOI: 10.1021/acsami.9b20154] [Citation(s) in RCA: 109] [Impact Index Per Article: 27.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
Organophoshorus nerve agents are among the most toxic chemicals known to humans, and because of their unfortunate recent use despite international bans, there is an urgent need to develop materials that can effectively degrade these nerve agents. Within the past decade, zirconium-based metal-organic frameworks (Zr-MOFs) have emerged as a bioinspired class of materials capable of rapidly hydrolyzing these compounds and significantly diminishing their toxicity. Both experimental and computational insights have guided the design of Zr-MOFs, leading to the development of catalysts capable of detoxifying nerve agents and simulants, chemicals with similar functionality but lower toxicity, via hydrolysis within seconds in basic aqueous solutions. While these systems are acceptable for the elimination of stockpile weapons, translating this catalytic performance to filters incorporating Zr-MOFs that can be used in masks or protective clothing is not trivial. As such, a large area of focus recently has been targeted toward integrating these hydrolysis catalysts into protective clothing and gear while retaining the performance from solution-based catalytic systems. This Forum Article provides an overview of the development of Zr-MOFs for the catalytic hydrolysis of organophosphorus substrates, including design principles and mechanistic insights for both solution-based and textile-coated systems. Finally, we highlight the remaining challenges yet to be addressed and offer perspectives on the future directions for this field.
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Halder A, Lee S, Yang B, Pellin MJ, Vajda S, Li Z, Yang Y, Farha OK, Hupp JT. Structural reversibility of Cu doped NU-1000 MOFs under hydrogenation conditions. J Chem Phys 2020; 152:084703. [DOI: 10.1063/1.5130600] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
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Noh H, Yang Y, Zhang X, Goetjen TA, Syed ZH, Lu Z, Ahn S, Farha OK, Hupp JT. Single‐Site, Single‐Metal‐Atom, Heterogeneous Electrocatalyst: Metal–Organic‐Framework Supported Molybdenum Sulfide for Redox Mediator‐Assisted Hydrogen Evolution Reaction. ChemElectroChem 2020. [DOI: 10.1002/celc.201901650] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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Kim IS, Ahn S, Vermeulen NA, Webber TE, Gallington LC, Chapman KW, Penn RL, Hupp JT, Farha OK, Notestein JM, Martinson ABF. The Synthesis Science of Targeted Vapor-Phase Metal-Organic Framework Postmodification. J Am Chem Soc 2020; 142:242-250. [PMID: 31851505 DOI: 10.1021/jacs.9b10034] [Citation(s) in RCA: 25] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The postmodification of metal organic frameworks (MOFs) affords exceedingly high surface area materials with precisely installed chemical features, which provide new opportunities for detailed structure-function correlation in the field of catalysis. Here, we significantly expand upon the number of vapor-phase postmodification processes reported to date through screening a library of atomic layer deposition (ALD) precursors, which span metals across the periodic table and which include ligands from four distinct precursor classes. With a large library of precursors and synthesis conditions, we discern trends in the compatibility of precursor classes for well-behaved ALD in MOFs (AIM) and identify challenges and solutions to more precise postsynthetic modification.
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